They are a 22-year-old from Birmingham, a 32-year-old arrested in Powys, and a 24-year-old from Northampton.

The latter was arrested in Cyprus and the Ministry of Defence had previously confirmed he was held at the island's British Dhekelia base before being transferred to RAF Akrotiri for a flight back to the UK.

More questioning

The men are being held on suspicion of being concerned in the commission, preparation and instigation of acts of terrorism under the Terrorism Act 2000; namely on suspicion of being members of a proscribed organisation.

A West Midlands Police spokeswoman said: "Detectives have been granted extra time to question the men."

Three of the servicemen are believed to be from the Royal Anglian Regiment.

Being a member of - or inviting support for - a proscribed organisation is a criminal offence carrying a sentence of up to 10 years in prison.